JAKARTA, Indonesia — The key to averting a health catastrophe emerging from the tsunami ruins will be basic hygiene — clean water and toilets — medical officials said Saturday, reporting no major disease outbreaks but warning the worst may be just around the corner.

Dirty drinking and washing water combined with lack of proper sewage disposal, they said, are a recipe for explosive outbreaks of life-threatening diarrhea diseases such as cholera, typhoid and dysentery, as well as some forms of hepatitis.

“These are the sort of diseases that could occur any time now,” Dr. Michelle Gayer, an infectious diseases specialist at the World Health Organization, said Saturday.

More than 123,000 people are reported dead and officials say the toll is likely to climb as more bodies are found. Most of the victims were killed by the massive tsunamis that smashed coastlines after a magnitude 9.0 earthquake last Sunday off Indonesia’s coast.

However, the United Nations has warned that disease may claim almost as many lives.

Hospitals left standing after Asia’s killer tsunami haven’t been swamped by severely injured survivors. Most casualties either have light wounds or are dead.

Little clean waterBut sources of clean water and sanitary toilets have been largely wiped out in many areas by the devastation of the tsunami in Southeast Asia.

The waterborne illnesses threatening the region are caused by bugs in traces of feces, which can easily end up in the mouth not only when people don’t wash their hands before eating or preparing food, but also if plates and utensils are washed in sewage-contaminated water.

A common way that such diseases get spread is by fetching buckets of water from rivers and lakes where people bathe and defecate.

“We don’t really know how the water is being supplied at the moment,” Gayer said. “If it (smells and looks) dirty, people tend to avoid it, but these organisms don’t make the water visibly dirty.”

“These things are completely preventable and they are reasonably easily preventable,” Gayer said. “In this case it’s a massive logistical nightmare, but it is possible to do it.”

Lack of nutrition a concernAccording to the World Food Program, there have been no reports of starvation in tsunami-stricken areas, and experts say they don’t expect a threat of starvation. There are food shortages in many areas, but not critical shortages.

However, a nutrition problem is emerging in the worst hit location at the northern tip of Sumatra, the Indonesian island nearest to the epicenter of the quake, said Dr. Georg Petersen, the WHO representative in Indonesia.

There is enough food coming in, but it’s mostly rice and noodles, which is not enough, even in the short term, to maintain the immune systems of the struggling survivors, he said.

Malnutrition increases vulnerability to infections. Efforts are under way, Petersen said, to bring in more nutritious food, such as high-protein biscuits.

Dead bodies are not a disease threat, scientists say.

The germs that cause the feared waterborne diseases die with their host, or within hours afterward. Cholera can survive a while, but most of the tsunami victims did not have cholera when they died, so their bodies would not be a health threat.

Medical experts say there are no disease-causing byproducts from the decomposition of human flesh.

Race to prevent diseaseA second health hazard wave will likely come from malaria and dengue fever, spread by mosquitoes that breed in stagnant water. Those illnesses, also life-threatening, are not expected to show up for another three or four weeks because it is too early now for the mosquitoes to proliferate and complete the cycle that spreads the diseases.

The impact of these two killers can also be stifled if shelters are sprayed with insecticides and if as many pools of water are eliminated as possible.

Besides water and sanitation, other priorities include shelter, food and basic medical services so that if people do get sick they can be treated quickly, reducing the risk that diseases will spread.

The United Nations Children’s Fund is coordinating much of the water and sanitation effort, preparing a mass distribution of emergency health kits that include water purification tablets and disinfectant.

Huge water containers called bladders, which carry 2,640 gallons each, are on their way to the hardest hit areas and technicians in water and sanitation are being drafted from around the world.

Bottled water is not considered sustainable after a while, especially because so many people need the water. The medium-term goal is to find a dam or lake locally that can provide water that can then be chlorinated by the aid agencies, trucked to various locations in huge bladders and distributed in a systematic way.